The long-term objective of this research is to delineate the neurological mechanisms underlying the development of visual anisotropy. Visual sensitivity is anisotropic in that adults in Western societies are better able to see horizontal and vertical contours than any other orientation. Since this increased sensitivity for horizontal and vertical information is of neural rather than optical origin, varies between ethnic groups, and is suscetible to environmental deprivation, anisotropy is a promising phenomenon for studying the effects of maturation and environmental variation on both behavior and neurophysiology. In the proposed project I will use two converging methods to measure the development of anisotropy between three years and adulthood. The psychophysical method tests the subjects' abilty to detect sinusoidal gratings in different orientations. The physiological method measures the cortical (surface) potential evoked by these gratings and is suitable for use with subjects of all ages, including children younger than three years. Once reliable, convenient methods for measuring anisotropy in humans over wide age ranges are established, the effects of environmental variations can be effectively studied.